Preparation process of photoinitiator methyl benzoylformate

Abstract

The invention discloses a preparation process of photoinitiator methyl benzoylformate, which comprises the following steps: carrying out bromination reaction on acetophenone serving as a raw material to obtain 2, 2-dibromo-1-phenylethanone; the method comprises the following steps: carrying out alcoholysis on 2, 2-dibromo-1-phenylethanone in a specific solvent under photocatalysis to obtain high-purity methyl benzoylformate; the preparation process has the advantages of easily available raw materials, mild reaction conditions and simple post-treatment, and is suitable for industrial production.

Description

Technical Field

[0001] The invention belongs to a preparation process of a photoinitiator, and more specifically relates to a preparation process of a photoinitiator methyl benzoylformate. Technical Background

[0002] This patent mainly aims to improve the defects of the existing preparation process of industrial photoinitiator methyl benzoylformate (MBF). The existing preparation methods of photoinitiator MBF mainly include the following preparation methods:

[0003] Using benzaldehyde as raw material: using benzaldehyde as raw material, reacting benzaldehyde with chloroform under alkaline conditions to obtain a product which is then oxidized with potassium permanganate to obtain benzoylformic acid; or treating benzaldehyde with sodium bisulfite and sodium cyanide to obtain benzoylnitrile, then hydrolyzing the benzoylnitrile and oxidizing it with potassium permanganate to obtain benzoylformic acid, and finally esterifying.

[0004] The above two methods are to prepare benzoylformic acid with benzaldehyde as raw material, which is expensive, has a low overall yield, and the highest overall yield is only 45.0%. In addition, using potassium permanganate as an oxidant will cause huge pollution, and sodium cyanide is very dangerous to use under acidic conditions.

[0005] Acetophenone is used as a raw material, reacted with chlorine gas, so that the chlorine atoms replace the two hydrogen atoms on the methyl group, and then treated with alkali and acid hydrolysis in sequence, and finally oxidized with potassium permanganate to obtain benzoylformic acid. Benzoylformic acid reacts with methanol to obtain methyl benzoylformate. The process route of this method is relatively long, the chlorine gas used is highly toxic, and the chlorination is a dangerous process reaction that is difficult to control. In addition, the use of potassium permanganate as an oxidant will produce a large amount of sewage, causing huge pollution.

[0006] Using dimethyl oxalate as raw material, it reacts with phosphorus pentachloride to obtain monomethyl oxalate dichlorosubstituted, which is further reacted with benzene to obtain MBF through Friedel-Crafts reaction. The preparation of the intermediate in this method uses a large amount of phosphorus pentachloride, has high requirements for equipment, high energy consumption, and complex post-processing; the second step Friedel-Crafts reaction requires the use of excessive aluminum chloride as a catalyst, which has severe acid corrosion and produces a large amount of three wastes, making post-processing difficult.

[0007] In view of the defects of the existing MBF process, the present invention provides a green synthesis process of MBF, which has easy-to-obtain reaction raw materials, mild reaction conditions, simple post-treatment and less three wastes, and is suitable for industrial production. Summary of the invention

[0008] The invention aims to provide a green preparation process of a photoinitiator methyl benzoylformate.

[0009] According to one aspect of the present invention, a process for preparing a photoinitiator methyl benzoylformate is provided, comprising:

[0010] (1) Acetophenone is subjected to an α-bromination reaction under acid catalysis to prepare 2,2-dibromo-1-phenylethanone;

[0011] (2) 2,2-Dibromo-1-phenylethanone is dissolved in a specific solvent and undergoes alcoholysis under photocatalysis to obtain methyl benzoylformate.

[0012] In some embodiments, acetophenone can be used to prepare 2,2-dibromo-1-phenylethanone without using a solvent or using a chlorinated alkane as a solvent.

[0013] In some embodiments, the catalyst used in preparing 2,2-dibromo-1-phenylethanone from acetophenone can be glacial acetic acid or concentrated sulfuric acid, and the amount used is 1-5 times the molar equivalent of acetophenone.

[0014] In some embodiments, the bromine source used in preparing 2,2-dibromo-1-phenylethanone from acetophenone can be liquid bromine or N-bromosuccinimide (NBS), and the amount used is 2-3 times the molar equivalent of acetophenone.

[0015] In some embodiments, the specific solvent used in preparing methyl benzoylformate from 2,2-dibromo-1-phenylethanone is dimethyl sulfoxide (DMSO), and the amount used is 5-30 times the molar equivalent of 2,2-dibromo-1-phenylethanone.

[0016] In some embodiments: the preparation of methyl benzoylformate from 2,2-dibromo-1-phenylethanone is carried out under irradiation of a mercury lamp.

[0017] In some embodiments, the amount of methanol used in preparing methyl benzoylformate from 2,2-dibromo-1-phenylethanone is 2-5 times the molar equivalent of 2,2-dibromo-1-phenylethanone.

[0018] In some embodiments, the reaction temperature for preparing methyl benzoylformate from 2,2-dibromo-1-phenylethanone is 25-75°C, preferably 55°C.

[0019] The outstanding features of the preparation process of the photoinitiator MBF of the present invention are:

[0020] (1) The raw material acetophenone is cheap and readily available, the entire preparation process is mild, and there are few wastes, so it is suitable for industrial production.

[0021] (2) The product is obtained by the next step of photocatalytic alcoholysis of 2,2-dibromo-1-phenylethanone. This is a non-hazardous process with a high process safety factor.

[0022] (3) The post-reaction treatment is simple, and the product can be obtained by simple distillation to recover the solvent and then distillation. DETAILED DESCRIPTION

[0023] In order to better understand the technical solution of the present invention, the above content of the present invention is further described in detail through specific embodiments, but it should not be understood that the scope of the above subject matter of the present invention is limited to the following examples. All technologies realized by the above content of the present invention belong to the scope of the present invention.

[0024] Embodiment 1

[0025] (1) Synthesis of 2,2-dibromo-1-phenylethanone

[0026] 60g of acetophenone was dissolved in 100ml of anhydrous acetic acid, and a mixed solution of 80g of liquid bromine and 50ml of acetic acid was added dropwise at 25°C. The reaction was exothermic and the reaction temperature was controlled to be 20-30°C. The generated hydrogen bromide was absorbed by alkali solution. After the reaction of the raw material was completed by TLC monitoring, 200ml of water was added to quench the reaction, and 133.6g of crude 2,2-dibromo-1-phenylethanone was obtained by washing and separation. The gas chromatography content was 96.7%, and it was directly used for the next step reaction without purification.

[0027] (2) Alcoholization of 2,2-dibromo-1-phenylethanone to obtain the photoinitiator MBF

[0028] 133.6 g of the crude 2,2-dibromo-1-phenylethanone obtained in the previous step was dissolved in 650 ml of DMSO, and 65 g of methanol was added, and the temperature was raised to 50-55° C. under irradiation of a 400 W mercury lamp to start the reaction. After the reaction of the raw materials was completed, nitrogen was introduced into the system to purge the generated hydrogen bromide and absorb it with alkali solution; then the temperature was raised to distill and recover the solvent. After the solvent was recovered, the product was separated by vacuum distillation, and finally 71.3 g of the product was obtained, with a gas chromatographic content of 98.8% and a product yield of 86.9%.

[0029] Embodiment 2

[0030] (1) Synthesis of 2,2-dibromo-1-phenylethanone

[0031] Dissolve 60g of acetophenone in 100ml of dichloroethane, slowly drop 48g of concentrated sulfuric acid, cool to 25°C after the dropwise addition, and start dropwise adding a mixed solution of 80g of liquid bromine and 50ml of dichloroethane. After the reaction ends, add 200ml of water to quench, wash with water to separate 136.2g of 2,2-dibromo-1-phenylethanone, with a gas chromatography content of 97.8%; use it directly in the next reaction without purification;

[0032] (2) Alcoholization of 2,2-dibromo-1-phenylethanone to obtain the photoinitiator MBF

[0033] 136.2 g of the crude 2,2-dibromo-1-phenylethanone obtained in the previous step was dissolved in 650 ml of DMSO, and 65 g of methanol was added, and the temperature was raised to 50-55° C. under irradiation of a 400 W mercury lamp to start the reaction. After the reaction of the raw materials was completed, nitrogen was introduced into the system to purge the generated hydrogen bromide and absorb it with alkali solution; then the temperature was raised to distill and recover the solvent. After the solvent was recovered, the product was separated by vacuum distillation, and finally 73.3 g of the product was obtained, with a gas chromatographic content of 99.1% and a product yield of 89.4%.

Claims

1. A process for preparing a photoinitiator methyl benzoylformate, characterized in that: include: (1) Acetophenone is subjected to an α-bromination reaction under acid catalysis to prepare 2,2-dibromo-1-phenylethanone; (2) 2,2-Dibromo-1-phenylethanone is dissolved in a specific solvent and undergoes alcoholysis under photocatalysis to obtain methyl benzoylformate.

2. The preparation process of the photoinitiator methyl benzoylformate according to claim 1, characterized in that: Acetophenone can be used to prepare 2,2-dibromo-1-phenylethanone without solvent or using chlorinated alkanes as solvent.

3. The preparation process of the photoinitiator methyl benzoylformate according to claim 1, characterized in that: The catalyst used in preparing 2,2-dibromo-1-phenylacetone from acetophenone can be glacial acetic acid or concentrated sulfuric acid, and the amount used is 1-5 times the molar equivalent of acetophenone.

4. The preparation process of the photoinitiator methyl benzoylformate according to claim 1, characterized in that: The bromine source used in preparing 2,2-dibromo-1-phenylacetone from acetophenone can be liquid bromine or N-bromosuccinimide (NBS), and the amount used is 2-3 times the molar equivalent of acetophenone.

5. The preparation process of the photoinitiator methyl benzoylformate according to claim 1, characterized in that: The specific solvent used for preparing methyl benzoylformate from 2,2-dibromo-1-phenylethanone is dimethyl sulfoxide (DMSO), and the amount of DMSO used is 5-30 times the molar equivalent of 2,2-dibromo-1-phenylethanone.

6. The preparation process of the photoinitiator methyl benzoylformate according to claim 1, characterized in that: The preparation of methyl benzoylformate from 2,2-dibromo-1-phenylethanone was carried out under the irradiation of a mercury lamp.

7. The preparation process of the photoinitiator methyl benzoylformate according to claim 1, characterized in that: The amount of methanol used in the preparation of methyl benzoylformate from 2,2-dibromo-1-phenylethanone is 2-5 times the molar equivalent of 2,2-dibromo-1-phenylethanone.

8. The preparation process of the photoinitiator methyl benzoylformate according to claim 1, characterized in that: The reaction temperature for preparing methyl benzoylformate from 2,2-dibromo-1-phenylethanone is 25-75°C, preferably 55°C.